Make stop complete notification call in to ActivityManager blocking.

This call can lead directly to Surface destruction, so it's only safe
to execute while the app renderer is paused. If the call is oneway and is
deferred we can end up in a scenario where the call is processed (destroying
the surface) after the client renderer has been unpaused for a different reason.

Bug: 80423392
Bug: 62536731
Test: Manual. go/wm-smoke.
Change-Id: Ide9da46a4ca7b6ef3b55c9966cc495b70b10fa46